c++ - 处理输入和输出的C++函数

Question

我被赋予了用c++编写代码的任务，我不得不开发一种算法，按照以下标准检查3个数字，如果第一个指数的第二个数字等于第三个数字，那么我应该返回true或false。我使用幂函数来查找第一个数字升为第二个数字，以及另一个称为comapare(num1，num2，num3)的函数。我的pogramme正常工作，但问题是它在控制台中显示了结果，我想输出到输出我将文件命名为outfile的文件，当我这样做时，我收到一条错误消息，指出未声明outfile，我将不胜感激，能够将其输出到输出文件。
下面是我的代码

#include <iostream>
#include<fstream>

using namespace std;

double powerfunc(double num1,double num2){ // power function  

    double base=num1,exponent=num2,result;//decalsring base and exponent

    for(int i=1;i<exponent;i++){
        base=base*base;
        result=base;
    }
    return result;
}

double compare(double x, double y,double z){//Comapares if x exponent y gives z and return 
    //Return true or false

    int storersults;
    if( (powerfunc(x,y)== z)){
        cout<<"true"<<endl;
        //outfile<<"true"<<endl;
        storersults=powerfunc(x,y);
        cout<<"results is "<<storersults;
        //outfile<<"results is "<<storersults;
    }
    else{
        cout<<"false"<<endl;
        //outfile<<"false"<<endl;
        storersults=powerfunc(x,y);
        cout<< " results is "<<storersults;
        //outfile<<"results is "<<storersults;
    }
    return storersults;
}

int main(){
    ifstream infile;
    ofstream outfile;

    infile.open(" input.txt");
    outfile.open("output.txt");// I wanna link output to functions above and get results // I wann get results on outputfile not on console
    // double a,b,c;
    //infile>>a,b,c;
    powerfunc(3,2);//This functions finds power of 3 and 2
    compare(3,2,9);//This fucnions compare if 3^2=9 then retuens true

    }
    infile.close();
    outfile.close();
    return 0;
}

Answer 1

您可以在想要执行输出的函数中接受输出流，如下所示:

double compare(double x, double y,double z, std::ostream &out) {
                                          // ^^^ accept some stream
  out << "hello"; // print whatever output to the stream
}

然后在main中，您可以这样调用它:

outfile.open("output.txt");
compare(3,2,9, std::cout);   // to print to console
compare(3,2,9, outfile);     // to print to file